Origin and Habitat: Rio Ocoña to Camana, Southern Coast of Arequipa, Peru.Altitude: 20-300 metres above sea level.Habitat: Grows together with Haageocereus decumbens in very dry desert areas where it almost never rains and where only the occasional sea fog drift inland.

Description:Eriosyce islayensis, formerly known as Islaya islayensis, is a small cactus with very woolly areoles end dark spreading spines, it is indeed very variable and has received many names, but it is clear from fieldworks that the different wild populations constitute a single but multiform species. Islaya brevicylindrica has shorter grey green cylindrical stems, but similar short cylindrical individuals can be found in other populations too, and also two plants of the same population can look very different. Islaya brevicylindrica, is generally included within (as a synonym of) Eriosyce islayensis, suggesting that there is not really a fundamental difference between the two.Stems: Initially globular, but slightly elongated to shortly cylindrical with age, grey-green, 5 to15 cm tall (rarely up to 70 cm tall), 5-10(-20) cm in diameter. Apex densely woolly.Ribs: 19-22 low and obtuse and more or less tuberculate.Areoles: Approximate, large, conspicuously woolly, with creamy-white to grey-brown felt.Roots: Fibrous.Spines: Variable in size and in colour whitish with reddish tips, changing to grey with age. Central spines: 1-3 spreading and markedly directed downward, thick, about 20 mm long.Radial spines: About 20, shorter, radiating, 7-10 mm long, but sometimes less than 3 mm long.Flowers: Diurnal, wide funnelform, yellow 1,5-2,5 cm long and in diameter (up to 4 cm in the variant known as grandiflora), born on younger areoles from a yellowish woolly crown in summer. Pericarpel and floral tube short scaly. Scales with tufts of dense wool and long reddish bristles. Petals yellow, sepaloids often orange or reddish. Style yellow.Fruits: Characteristic, up to 5 cm long, club shaped, balloon-like, pinkish to red, when mature inflated, openings by basal pores. Pericarp initially fleshy but the interior always dry when mature.Seeds: Broadly oval.

Subspecies, varieties, forms and cultivars of plants belonging to the Eriosyce islayensis group

Eriosyce islayensis(C.F.Först.) Katt.: has globose to cylindrical stems with very woolly areoles and dark spreading spines, the different wild populations constitute a single but multiform species. Distribution: Northern Chile along the coast, to southern Peru (just south of Lima)

Islaya krainzianaF.Ritter: has strong somewhat columnar stems that can reach 75 cm high (the taller of the islayas). Distribution: It is the only Chilean population of "Islaya", located around Poconchile above Arica, very near the Peruvian border.

Islaya longicarpaKníže: has very long fruits. Distribution: along the coast near Atico, Peru.

Notes: Eriosyce islayensis has a large area of distribution and is a very variable species. The difference between populations is the frequency of the appearance in which these forms do occur. So it is possible that two individuals of two different populations can look very similar and also, that two plants of the same population can look very different. However when you are looking at the whole population, you can see the difference between one population and another.

Cultivation and Propagation: It is an extremely xerophytic, summer-growing, species adapted to very dry soils that, like many cacti of the Peruvian deserts, present some problems in cultivation. It is in fact somewhat rot prone if kept in a non ventilated place. Growth rate: Slow-growing.Soil: It requires a very fast draining drying open mineral, sandy-gritty cactus composts. Provide a very good drainage. Exposure: It is suited for sunny-brightly exposure, but can tolerate light shade. However it will do its best only with lots of sun and become stressed with inadequate light which could result in poor growth and unnatural shape. It has a good heat tolerance. Watering: Water regularly in summer, but do not over-water and keep it completely dry during winter. Mature individuals easily rot and die especially after transplanting so be extremely cautious with watering. Keep dry in winter or when night temperatures remain below 10° C. Water it less than average if in bigger pots.Fertilization: Feed them once during the growing season with a fertilizer specifically formulated for cactus and succulents (high potash fertilizer with a dilute low nitrogen), including all micro nutrients and trace elements diluted to ½ the strength recommended on the label. They thrive in poor soils and need a limited supplies of fertilizer to avoid the plants developing excess vegetation, which is easily attacked by fungal diseases.Special need: It is suited for airy exposures. Provide very good ventilation. Nearly all problems occur as a result of overwatering and poor ventilation, especially when weather conditions are dull and cool or very humid. They must have very dry atmosphere.Hardiness: It likes warmth (recommended minimum winter temperature 5° C), but hardy to at least -5°C (it can probably tolerate freezing temperatures down to -10° C for brief periods) It has a good heat tolerance.Pests & diseases: These cacti may be attractive to a variety of insects, but plants in good condition should be nearly pest-free, particularly if they are grown in a mineral potting-mix, with good exposure and ventilation. Nonetheless, there are several pests to watch for. - Red spiders: Red spiders may be effectively rubbed up by misting the plants from above. - Mealy bugs: Mealy bugs occasionally develop aerial into the new leaves and flowers with disfiguring results, but the worst types develop underground on the roots and are invisible except by their effects. - Scales, thrips and aphids: These insects are rarely a problem. - Rot: Rot is only a minor problem if the plants are watered and “aired” correctly. If they are not, fungicides won't help all that much.Propagation: Usually propagated from seeds (seldom produces offsets) or graft. The seeds can be sown in pots of fine, well-drained sandy soil, any time during the spring when temperatures are warm. Cover the seeds with a fine layer of grit and water from below with a fungicide to prevent damping off. For the 1-2 weeks cover the pots with a sheet of glass/clear perspex to keep the humidity levels high. Remove the glass and replace it with light shade-cloth and mist once or twice a day for the next two weeks after which most seeds should have germinated. From then on mistings can be reduced to every second and then every third day as the little plants grow. The seedlings should not be disturbed until they are well rooted after which they can be planted separately in small pots. Sometimes it is grafted onto a strong grafting stock like Selenicereus sp. to avoid root rot problems as plants grafted on an hardy stock are easy to grow and no special skill is required. Such grafted seedlings can be been successfully cultivated for years. Mature plants imported from the native habitats usually did not take roots and dyes in a few months.